If there aren't any other plans for these delicious artifacts, I would suggest putting more radiant fire crystals in them. That alone would make me actually go out of my way to get them, and actually going to get them is in this case a definite problem- with no rarities they are worth less than the boxes at the end and are worth skipping outright when they could rather be extra credit or perhaps a main object in some later update.
Boxes in the core are going to need a bit more than just crowns and heat
It would be cool.if all of these artifacts were collecting was a part of a huge device that wouod be used to either kill or seal the swarm after defeating ot. Because just collecting useless junk just not good enough to keep them in our inventory.
Would be neat if they dropped a unique kind of token in all honesty. Tokens would be exchangeable for various items at either the end of the mission or in some addition later on. Could be traded for rarities (1 token = 1 radiant, 3 shining, 8 glowing, 18 dim), materials, maybe even slot upgrades at very high amounts. You could also get some crown value out of them, such as 100 crowns per token.
I dunno. Something that makes them worthwhile for sure. Ensuring you get radiants is a better track to take than hoping you get them anyways.
Where my darkfang shield at?